In the nematode Caenorhabditis elegans, several groups of small molecules control genetic pathways as intrinsic molecular messengers. A group of glycosides, the ascarosides, have recently been shown to induce development arrest (dauer formation) and, furthermore to act as sex pheromones. Our preliminary results show that ascarosides not only act as dauer or mating signals, but also strongly influence adult lifespan and thermotolerance. Therefore, ascaroside signaling provides a direct link between developmental arrest and aging, and offers a unique set of tools to identify and probe the corresponding molecular pathways. The principal goal of this proposal is to determine the genetic pathways involved in ascaroside-mediated increases in Lifespan and thermotolerance. For this purpose synthetic samples of the endogenously produced ascarosides will be employed in a novel approach that combines chemical genomics with recently acquired knowledge about the biological roles of these signaling molecules. Using synthetic samples of the eight so-far identified ascarosides, the effect of various concentrations and combinations of these compounds on thermotolerance and lifespan in the wildtype worms will be determined. Subsequently, ascarosides or ascaroside-combinations with strong thermotolerance or lifespan phenotypes will be assayed in additional thermotolerance assays against a selection of mutants of key genetic pathways known to be involved in aging and development. These targeted studies will be complemented by global gene expression studies to reveal additional genetic pathways that are up or down regulated upon exposure to ascarosides. Follow-up will include additional thermotolerance assays using available mutants or knock-down of affected genes of interest. Results from these investigations will allow us to develop a comprehensive research program targeting specific aging-relevant pathways modulated by ascarosides. It seems likely that many aspects of these pathways are conserved through species, providing incentives for further study of corresponding pathways in other organisms. Moreover, the proposed study could represent a model for the use of endogenous small molecules to probe signaling networks in C. elegans and other organisms. PUBLIC HEALTH RELEVANCE: The pervasive physiological changes associated with aging are reflected in age-dependent increases in the incidence of many diseases, including, diabetes, cancer, neurological disorders, heart disease, and osteoporosis. In nematodes, endogenous compounds called ascarosides have been shown to significantly retard the effects of aging and increase lifespan. The proposed study aims to investigate the biological mechanisms through which the ascarosides increase lifespan in nematodes, which will contribute to our understanding of the causes of aging in humans.